You may have corrupt sessionstore [v56] sessionstore.jsonlz4 file(s). Delete all sessionstore* files and the sessionstore-backups folder.

Type about:support<enter> in the address bar.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder

Linux: Under the page logo on the left side, you will see Application Basics. Under this find Profile Directory. To its right press the button Open Directory.

Locate the above file. Then rename or delete it. Restart Firefox.

Don't delete the files if you need to rescue any data from them, just move them out of the profile folder to some location where Firefox doesn't look for them. You can try to read out their contents using this tool: https://www.jeffersonscher.com/res/scrounger.html

illcastellano said

All of the sudden, Firefox shut down

Please explain the problem in detail. What happens? What are the exact error message(s) ? Have you checked for crash reports?

For more help on crash reports, see; https://support.mozilla.org/en-US/kb/firefox-crashes-asking-support

thank you. I restarted my computer and followed your directions, and everything went back in order. Thank you so much!

btw, I didn't receive any error message. I was using excel, and firefox shut down. when I opened it again, I just had the regular home page.

Keep an eye out for trouble and let us know.